There is known a welder (cf. USSR Inventor's Certificate No. 491,458) for welding articles with circumferential seams, comprising a movable bed, whereupon there is mounted an axially movable welding head with a drive, a means for pressing butt ends of components being welded against one another, and a mechanism for rotating said means.
The welder under review is applicable for butt welding of tubular articles without corrugations on their lateral surfaces.
However, in the case of welding corrugated bellows sections it is impossible to match and firmly press together the butts of sections being welded, which, in turn, makes it impossible to produce a high-strength seam. The disadvantage is due to the fact that the welder under review lacks a clamping means for pressing together the butts of corrugated sections being welded.
There is known a clamping means for welding bellows sections with circumferential seams (cf. USSR Inventor's Certificate No. 439,365). The clamping means comprises a base carrying an axle to accommodate bellows sections, a mechanism for pressing together and locking in place bellows sections, and a drive for rotating sections being welded. Said mechanism has a common drive for the locking and pressing means. These are composed of separate members so that sections being welded are not matched and pressed together over their entire butt perimeters.
The means under review makes it possible to press together and lock in place bellows sections with a diameter of 94 mm and wall thickness of 0.1 mm.
However, this means does not make it possible to weld bellows sections with thinner walls and diameters of more than 100 mm.
Besides, the clamping means under review has a limited working space, whereby the production of long bellows is either impossible or calls for a clamping means of inordinate dimensions.
There is known a welder for welding large-size articles of the shell type, comprising a bed carrying a drive for rotating an article being welded and a means for pressing together the butts of articles being welded, composed of two chucks, whereof one is installed in a stationary support and connected to the rotation drive, whereas the other is installed in a movable support. The welder further includes a pneumatic cylinder interacting with the movable support, and a leg carrying a welding torch movable along a horizontal beam.
On this type of welder, bellows sections are rotated while being welded together. The sections are fixed between the driver chuck and the driven chuck and rotated by the drive of the driver chuck. In the course of welding, the edges being welded together may get misaligned or skewed with respect to each other; both effects may take place simultaneously.
Besides, the welded bellows portion is cantilevered with respect to the bellows sections being welded, which accounts for undesirable stresses in the weld area and affects the quality of the weld.
The conventional welders are not fit for high-quality welding of thin-walled, large-size bellows sections with circumferential seams because they are unable to firmly press together the butts of sections being welded over their entire perimeter. It must be remembered in this connection that a gap even of a few hundredths of a millimeter seriously affects heat removal and may cause a burn-through. The latter of the two welders under review does not ensure an accurate centering of the outer diameters of sections being welded, nor does it provide for an accurate positioning of the butt plane, which means that the weld plane does not always extend at a perpendicular to the longitudinal axis of the article being welded. This factor also affects the quality of welding and calls for additional means to control the mutual positioning of the welding head and the weld, which, in turn, complicates the overall design of the welder.
The absence of simple and reliable welders, which would provide for high-quality welding of large-size, thin-walled bellows sections, makes it extremely difficult to manufacture large-size, thin-walled bellows and bellows units of stainless steel, having a wall thickness of 0.1 to 0.3 mm and a diameter of 200 to 800 mm.